1. Field of the Invention
The present invention relates to a switch device and, more particularly, to a switch device suitable for a horn switch that is mounted on a pad part of a steering wheel.
2. Description of the Related Art
A conventional switch device typically has a structure in which a knob part is held in a vertically movable manner in a case via a link member which pivots on an operating body, and in which movable contacts are held on a printed board so as to surround fixed contacts formed on the printed board. In this type of structure, the knob part is urged upward by the elastic force of the movable contacts. In this state, when the knob part is pressed; the movable contacts come in contact with the fixed contacts so that the electrical connection therebetween are established (for example, see Japanese Unexamined Patent Application Publication No. 2003-123575).
Hereinafter, the structure of a conventional switch device will be described with reference to the exploded perspective view shown in FIG. 6.
In FIG. 6, the switch device comprises a printed board 31, an elastic sheet 34, a case 36, an operating body 37, a link member 38, and a knob part 39.
A fixed contact 32 is printed on the printed board 31, and an LED 33 is placed adjacent to the fixed contact 32. The elastic sheet 34 is made of a rubber material and is composed of a sheet-like base part 34a and an operating part 34b protruding from the base part 34a. A movable contact 35 is formed below the operating part 34b. The case 36 is made of a synthetic resin and consists of a top wall 36a with an opening 36c and engaging pawls 36e, and a sidewall 36b. 
The operating body 37 is made of the same synthetic resin and consists of an elongated rectangular base part 37a, a protruding part 37c that projects upward, and a hollow part 37d penetrating through both the base part and the protruding part. Further, a circular pressing part 37e is provided below the base part 37a, and cut recesses 37f are provided above the protruding part 37c. The link member 38 is a metallic wire rod and is composed of a longitudinal side 38a, connecting arms 38b bent at both ends of the longitudinal side 38a, and protruding parts 38c. The knob part 39 is made of a synthetic resin and consists of a top wall 39a, elongated sidewalls 39b, and projections 39c that are provided on the underside of the top wall 39a. 
The elastic sheet 34 is placed on the printed board 31 having the above structure. The operating body 37 is placed on the elastic sheet 34 so that the operating member 34b and the pressing part 37e are opposite to each other. The case 36 is attached to the printed board 31 in such a way that the protruding part 37c projects upward through the opening 36c. The link member 38 engages with the engaging pawls 36e so that the protruding parts 38c are fitted into the recesses 37f of the operating body 37. Then, the protruding parts 38c of the link member 38 are pivotally sandwiched between the protrusions 39c of the knob part 39 and the recesses 37f. 
In the switch device having the above structure, when the knob part 39 is pressed, the link member 38 pivots, and the operating body 37 are compressed by the operating part 34b, thereby operating the switch. At this time, the longitudinal side 38a of the link member 38 is parallel to the longitudinal direction of the operating body 38. Therefore, even if any portion of the knob part 39 is pressed, the operating body 37 is vertically operated, thereby assuring the reliable operation of the switch device.
However, the complex structure of a conventional switch causes assembly to be difficult due to many components. There is also a problem of increased cost of the switch device due to the use of a link member.